I think what the NCLEX is looking for is the fact that LPNs aren't supposed to make judgement calls that could have a major impact on patient outcomes. For instance, you wouldn't tell the LPN to go do the admission assessment on the new MICU patient who is septic, hypotensive, tachycardic, febrile, and anuric. In NCLEX world, the LPN is supposed to do things that don't involve making a judgement based on their assessment. LPNs can't do initial admission assessments, they can't do initial patient teaching, and in my state, NC, they can't administer blood or blood products. An LPN can do an assessment on a patient who has been an inpatient for some length of time, but the LPN cannot make a judgement call. For instance, say you have a patient who is on the cardiac step-down unit four days post CABG. The LPN can go in and do the assessment, to my knowledge, but if something is wrong, it must be reported to the RN. Suppose the LPN found the patient febrile and tachycardic, s/he couldn't assume it was the beginning of an infection, make a note in the chart, notify the physician, and go on about the day. If the LPN found a significant piece of data such as I mentioned in my example, s/he would have to go to the RN and report what s/he noted on assessment. For instance, "Nurse Smith, upon assessing room 8422, I noted that he was tachycardic at a rate of 125 and that he had a fever of 101.2." This is all the LPN can do. S/he can't say, "I think the patient is developing an infection, and we need to notify the physician and draw blood cultures." That responsibility lies solely with the RN.
Based on what I've been taught, LPNs can assess stable inpatients who have been in the hospital for some period of time. It doesn't matter if they've been there ten hours or ten days. I was taught that LPNs can't do the initial admission assessment, and can't do discharge teaching. The normal day-to-day head-to-toe assessments can be delegated to the LPN. We were also cautioned by one of our instructors to avoid choosing answers that have LPNs doing an activity that would require a judgement call, like changing a dressing on a fresh surgical site, etc. Our instructor said that, while the LPN may be able to do this, s/he can't make a judgement call about whether it looks normal, infected, etc, and that it would be our best bet to play it safe and avoid choosing these type of answers.
In reality, LPNs do things that require judgement calls. A skilled and experienced LPN is often just as adept at making judgement calls as an RN. In NCLEX land, however, the scope of LPN practice is severely limited. You could look up the scope of LPN practice in your state on the Board of Nursing website. This may help you determine the kinds of things that LPNs can and cannot legally do in your state. Having this information may help you when you answer questions about delegating to an LPN.